Move include/posix/io_posix.h to util/io_posix.h

Summary: include/posix/io_posix.h is not a public API. Although include/posix/ is not a public header directory, it is confusing to put non-public headers to under include/. Move it to util/ to be clearer.

Test Plan: Run all tests

Reviewers: rven, IslamAbdelRahman, anthony, kradhakrishnan, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D49611

util/env_posix.cc

@@ -39,9 +39,9 @@
 #include <deque>
 #include <set>
 #include "port/port.h"
-#include "posix/io_posix.h"
 #include "rocksdb/slice.h"
 #include "util/coding.h"
+#include "util/io_posix.h"
 #include "util/iostats_context_imp.h"
 #include "util/logging.h"
 #include "util/posix_logger.h"

util/io_posix.cc

@@ -9,7 +9,7 @@
 
 #ifdef ROCKSDB_LIB_IO_POSIX
 
-#include "posix/io_posix.h"
+#include "util/io_posix.h"
 #include <errno.h>
 #include <fcntl.h>
 #if defined(OS_LINUX)